A Single-Chain Antibody (SCA) protein with catalytic activity will be prepared. The SCA protein will be designed form the variable region sequences of one of two antibodies found to have lipase activity, either 2H6 ro 21H3. A gene to synthesize this protein will be constructed and the protein will be expressed in E. coli. The protein will be renatured, purified, and assayed for its enzymatic activity. This SCA protein will be engineered to have increased stability and increased catalytic activity during Phase II of the project. The SCA protein with catalytic activity provides the means to accomplish genetic changes and determine the effect of catalytic activity and stability.